Process of color separation in lithography



June 1, 1943. J. CUNNINGHAM 2,320,914

PROCESS OF COLOR SEPARATION IN LITHOGRAPHY Filed Jan. 29 1942LITHDERAPHY INVEN TOR. 22/115 @N/W/Vfi/MM Patenteii June 1, 1943 UNITEDSTATS PROCESS OF COLOR SEPARATHON IN LITHOGRAPHY James Cunningham, NewYork, N. Y., assignor of twenty per cent to Michael Dichiaro, Brooklyn,

Application January 29, 1942, Serial No. 4282699 4 Claims.

This invention relates to ration in lithography.

In the present method employed in the separation of color in thelithograph industry, each color must be opaqued out. In the reproductionprocess of color sepaof a two color job, for example, red and blue, the

original copy is set on the copy board in the camera department and anegative is then made from the same. The negative is then stripped orplaced in position on glass or Celluloid, or any other material suitablefor reproduction of the negative.

The negative then goes to the opaquing department where the colorseparation takes place. To prepare or opaque said negative for redplate, the part of the negative which is to be reproduced in blue isfirst opaqued out. The negative then goes to the sensitized emulsionplate department, and a contact sensitized emulsion plate is made fromthe same. This plate only reproduces the part which has not been opaquedout and is hence, the red plate.

The negative is then returned to the opaquing department. The part whichwas previously opaqued out (the part to be reproduced in blue), is thenwashed clear of the opaque previously applied. The part which is to bereproduced in red is then opaqued out, and the negative again gOes backto the sensitized emulsion department,

and a contact sensitized emulsion plate is made from the same toreproduce the part which is to be reproduced in blue. Thus, each part tobe reproduced must be successively opaqued out.

It is therefore an object of the present invention to partiallyeliminate the opaquing process,

so that in a red, blue job, for example, only the part to be reproducedin one color is to be opaqued out and not the other.

A further object of this invention is to provide a highly economical andefficient process of the character described, which shall be easy tocarry out, and practical to a high degree in use.

Other objects of this invention will in part be obvious and in parthereinafter pointed out.

The invention accordingly consists in the combination of steps, featuresof construction, combinations of elements, and arrangement of partswhich will be exemplified in the process and construction hereinafterdescribed, and of which the scope of application will be indicated inthe following claims.

In the accompanying drawing, in which is shown one of the variouspossible illustrative embodiments of this invention,

Fig. 1 is a top plan view of a collodion negative;

Fig. 2 is a top plan view of the negative, with dye applied to thesurface of the negative to be reproduced in red; and

Fig. 3 is atop plan view of the article shown in Fig. 2, with a yellowglass plate on top of it.

Fig. 4 is a cross section on the line 44 of Fig. 3.

In accordance with the present invention, one of the opaquing steps iseliminated. The process necessitates the use of a photo-engravers wetplate or collodion coated negative. The collodion negative isnecessarily a part of this process as it forms a base to which asaturated solution consisting of fuchsine crystals in methyl alcohol, adye applied in the process, adhere.

The process of reproducing of a two color job, red and blue, inaccordance with the present invention, will now be described, as anexample of the process.

The original copy is set on the copy board in the camera department anda negative is then made from the same. The negative is preferablycollodion covered. The negative is then stripped or placed in positionon glass or Celluloid, or any other substance suitable for thereproduction of the same.

The negative then goes to the opaquing department where the colorseparation takes place. To prepare or opaque said negative for redplate, opaque out the part of the negative which is to be reproduced inblue. The negative then goes to the sensitized emulsion platedepartment, and a contact sensitized emulsion plate is made from saidnegative. This plate only reproduces a part of the negative which wasleft clear and which is to be reproduced in red.

Up to this point, the process is substantially the same as the processused heretofore in two color lithography. However, with the presentinvention, the negative is then returned to the opaquing department,where a saturated solution comprising fuchsine crystals in methylalcohol is applied to the part of the negative which is to be reproducedin red. After this dye or solution has been applied to the negative, thepreviously opaqued part is washed oil, leaving the part to be reproducedin blue clear.

In accordance with the present invention, furthermore, a yellow glass isplaced over the negative in the printing frame. Instead of using ayellow glass, the same results may be achieved by stripping the negativeon a yellow glass or Celluloid instead of on clear glass or Celluloid,or by covering the clear transparent glass on which the negative isstripped with yellow Cellophane or Celluloid, or by any other yellowsubstance through which light can penetrate.

I have found that the combination of the red dye, comprising (saturatedsolution of fuchsine crystals and methyl alcohol) and the yellow glassor yellow Celluloid or Cellophane, prevent formation of an image on theemulsion plate in the normal time exposure allowed for the reproduction.Thus, the use of the dye and the alcohol glass or Celluloid orCellophane takes the place of the second opaquing process heretoforeused.

After the dye is applied to the part to be reproduced in red, thenegative is again returned to the sensitized emulsion department, and ai contact sensitized emulsion plate is made from the same. As statedabove, this plate will only reproduce the part to be reproduced in blueand not the part to which the dye has been applied.

In the drawing, l designates a collodion covered negative.

'In Fig. 2, the negative is shown with the dye ll applied to the part tobe reproduced in red, leaving clear the part l2 to be reproduced inblue.

In Fig. 3 there is shown a plate IA of glass applied over the negative.

It will thus be seen that there is provided a device and process inwhich the several objects .of this invention are achieved, and which iswell adapted to meet the conditions of practical use.

As various possible embodiments might be made of the above invention,and as various changes might be made in the embodiment above set forth,it is to be understood that all matter herein set forth or shown in theaccompanying drawing is to be interpreted as illustrative and not in alimiting sense.

Having thus described my invention, I claim as new and desire to secureby Letters Patent:

1. A process of the character described, consisting in opaquing out apart of a negative to be reproduced in one color, then applying acontact sensitized emulsion plate to the negative to make a printtherefrom of the part of the negative which has not been opaqued; thenapplying to the part of the negative which has not been opaqued, a dyeconsisting of fuchsine crystals dissolved in methyl alcohol, and washingout the opaquing on the part which has been previously opaqued, placinga yellow plate over the negative, and then making a contact sensitizedemulsion plate from the negative to reproduce on the second contactsensitized emulsion plate, the part of the negative which was originallyopaqued, and from which part the opaquing was washed away.

2. A process of the character described, consisting in making anegative, then opaquing out part of the negative, then printing a platefrom the negative to reproduce the part which has not been opaqued out,then applying a solution of fuchsine crystals to the part of thenegative which was not opaqued out, and then removing from the negativethe opaque previously applied to the part which has been opaqued out.

3. A process of the character described, consisting in making anegative, then opaquing out part of the negative, then printing a platefrom the negative to reproduce the part which has not been opaqued out,then applying a solution of fuchsine crystals to the part of thenegative which was not opaqued out, then removing from the negative theopaque previously applied to the part which has been opaqued out, andsuperimposing a yellow light transmitting memher over the negative.

4. A process of the character described, consisting in making anegative, then opaquing out part of the negative, then printing a platefrom the negative to reproduce the part which has not been opaqued out,then applying a solution of fuchsine crystals to the part of thenegative which was not opaqued out, then removing from the negative theopaque previously applied to the part which has been opaqued out, andsuperimposing a yellow light transmitting member over the negative, andthen making a print from the negative to reproduce the part to which thesolution was not applied.

JAMES CUNNINGHAM.

